One common theme is loyalty. Given their military background in the Halo universe, loyalty to each other and their comrades is often explored. Another is sacrifice. They are both characters who are willing to put themselves in harm's way, and this is often a big part of the stories.
A theme that frequently shows up is the struggle between duty and personal feelings. They have important military duties, but also growing feelings for each other. And of course, the theme of heroism. Master Chief and Linda are both heroes, and their heroic deeds are often central to the fanfics, sometimes in the face of seemingly impossible odds.
One common theme is adventure. Given the nature of the Halo universe, many fanfictions will have the characters embark on dangerous missions, like exploring new planets or fighting against the Covenant. Another theme is friendship and camaraderie among the characters. Master Chief, Linda, Kelly, and Lemon likely have strong bonds in these stories.
Love and friendship are also prevalent themes. Some fanfics might develop a romantic relationship between them, while others focus on their strong friendship. They are often portrayed as having a special bond that goes beyond the typical soldier - AI relationship. In addition, adventure and fighting together against the Covenant is another theme. They are in the middle of a war in the Halo universe, and fanfics might detail their battles side by side, with Cortana providing crucial support to Master Chief.
One great 'Master Chief x Linda fanfic' is 'The Bond Beyond Battle'. It beautifully portrays their relationship in the context of the Halo universe. Another is 'Linda's Perspective' which gives a deep look into how Linda views Master Chief and their shared experiences.
One common theme is the clash of cultures. Master Chief comes from a very different, militaristic background compared to the more diverse and sometimes chaotic RWBY universe. Another theme is teamwork. Fans like to write about how Master Chief and the RWBY characters can work together to overcome challenges.
One common theme is adventure. Given their roles in the Halo universe, many fanfictions feature them going on dangerous missions together, fighting against the Covenant or other threats.
One common theme is the 'forbidden love' aspect. Since Master Chief is a Spartan with a lot of responsibilities, a relationship might be against the rules or dangerous. Another theme is 'love against all odds', where he falls in love in the midst of a war - torn Halo universe. And sometimes, there's the theme of 'finding love in unexpected places', like with an alien species or a non - combatant in the Halo setting.
Another theme could be the exploration of teamwork. RWBY characters are used to working in teams, and Master Chief is often part of military operations. Fanfictions might explore how they would form a new team together, with different skills and personalities coming together. It could involve things like strategizing for battles, with the RWBY characters' unique abilities and Master Chief's combat expertise.
Another theme is the discovery of self - worth. The OC usually starts out feeling a bit lost or unimportant, but through their experiences with the Master Chief, they find their place and purpose. For example, in some stories, the OC discovers they have a unique skill that is crucial for the mission. It's a way of showing personal growth within the story.
One common theme is the clash of different worlds. Since it's a crossover, Master Chief often comes from his Halo universe into a new and different setting. This leads to him having to adapt, and in the process, a romantic relationship might form as he meets someone from that new world.
One common theme could be the exploration of his character in a different light, showing his vulnerability in a gay relationship. Another might be how he deals with his identity within the context of the Stranger Things world.